1. Field of the Invention
The present invention relates generally to a disk apparatus, and more particularly to a disk apparatus for writing data to and reading data from a rotating floppy disk by movement of a head carriage.
2. Description of the Related Art
Conventionally, floppy disk apparatuses are widely used in personal computers as external memory devices. In recent years, in an effort to cope with the coming video age, floppy disk apparatuses have begun to be developed that greatly expand memory capacity from the current 1.44 MB to 200 MB or more. In order to expand memory capacity to such a large extent, it is necessary to increase the current 300 rpm rotation speed of the floppy disk by 10 times or more and at the same time increase the current track density of 135 tracks per inch (hereinafter tpi) by 10 times or more, to 2,000 to 3,000 tpi. In order to reliably write and read data under these high-speed, high-density conditions, a high degree of precision is required of the head carriage drive so as to position the magnetic heads with a high degree of precision.
FIG. 7 shows a head carriage drive mechanism 10 for a conventional high-density floppy disk device. The head carriage drive mechanism 10 has a head carriage 11. The head carriage 11 has a head 12 and is moved and positioned longitudinally in the Y1-Y2 direction along a radius of a rotating floppy disk 17 by a first voice coil motor 13 and a second voice coil motor 14 (hereinafter referred to collectively as first and second voice coil motors 13, 14) provided on either side of the head carriage 11 while being supported by guide rods 15 and 16. The first voice coil motor 13 comprises a magnetic circuit structure 23 including a permanent magnet 20 and yokes 21 and 22, and a drive coil 24 fitted to yoke 22 and fixedly mounted on the head carriage 11. The second voice coil motor 14 comprises a magnetic circuit structure 33 including a permanent magnet 30 and yokes 31 and 32, and a drive coil 34 fitted to yoke 32 and fixedly mounted on the head carriage 11. The head carriage 11 moves longitudinally along the Y1-Y2 axis in accordance with the drive current sent through the drive coils 24 and 34. The wire of drive coil 24 and the wire of drive coil 34 have an identical diameter. Further, drive coil 24 and drive coil 34 have an identical number of turns so as to generate an identical propulsive force.
The head carriage drive mechanism 10 shown in FIG. 7 has a signal wire 40, an end of the signal wire 40 being attached to the head 12 and extending from the head 12 along an upper surface of the head carriage 11 in the horizontal X2 direction at a position indicated as 41 in the diagram. The signal wire 40 has an extended section 40a having a length adequate to not restrict the movement of the head carriage 11. The head carriage 11 is moved while moving the extended section 40a of the signal wire 40 (hereinafter extended signal wire section 40a).
At this point, it may be helpful to consider an X2-side load and an X1-side load arising when the above-mentioned head carriage 11 is moved longitudinally in the Y1-Y2 direction. The X2-side load is greater than the X1-side load because the extended signal wire section 40a provided on the X2 side must be dragged in addition to the head carriage 11, thus creating a load imbalance between the X2 side and the X1 side of the head carriage.
Despite the existence of this load imbalance, however, the first and second voice coil motors 13, 14 generate the same propulsive force. As a result, the precision with which the head carriage 11 is driven may deteriorate. In the case of a high-density disk with a track density in the range of 2,000 to 3,000 tpi, even a slight deterioration in the precision with which the head carriage 11 is driven can affect the accuracy and reliability with which data is written to or read from the disk.
Accordingly, it is an object of the present invention to provide a disk apparatus in which the problems described above are eliminated.
The above-described object of the present invention is achieved by a disk apparatus comprising:
a frame;
disk rotating means for supportably rotating a floppy disk;
a head for writing data to and reading data from a disk being rotated by said disk rotating means;
a head carriage for holding said head, said head carriage being movable in a direction of a radius of a disk supported by said disk rotating means; and
a first voice coil motor and a second voice coil motor for moving said head carriage provided on both sides of said head carriage, the first voice coil motor and second voice coil motor each respectively comprising:
a magnetic circuit structure mounted on said frame; and
drive coils mounted on said head carriage,
wherein said first voice coil motor generates a propulsive force on a first side of said head carriage corresponding to a load arising on said first side when said head carriage is moved, and said second voice coil motor generates a propulsive force on a second side of said head carriage corresponding to a load arising on said second side when said head carriage is moved.
The side on which the load is greater when the head carriage is being moved is driven with a propulsive force larger by just that greater load amount. Accordingly, each side of the head carriage is driven with a propulsive force corresponding in strength to the load on each side, that is, with a propulsive force that differs between the sides by an amount corresponding to the imbalance in load between the two sides.
As a result, it becomes possible to drive the head carriage with better precision and thus position the magnetic head with better precision than when the head carriage is driven with an identical propulsive force on each side. As a result of this more precise positioning, data can be accurately and reliably written to and read from even high-density disks having a track density in the range of 2,000 to 3,000 tpi.
Additionally, the above-described object of the present invention is achieved by the disk apparatus described above, wherein the first and said second voice coil motors are configured so that a number of turns in the drive coil of the first voice coil motor and a number of turns in the drive coil of the second voice coil motor differ so as to generate different respective propulsive forces corresponding to unequal loads on the two sides of the head carriage.
It is possible to alter the settings of the propulsive forces of the first and second voice coil motors, respectively, simply by changing the number of turns of the respective drive coils thereof, making it possible to flexibly accommodate changes in design.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.